Try unplugging a drive and booting up. You may get a message that system settings have changed. If so, then you should get a choice of two keys, one to accept changes and another to enter setup. I have three different Compaq "Diagnostics" disks which I can e-mail if that doesn't work.
Try hitting the "F10" key at boot, if that doesn't work, you'll need to download Compaq's "F10 setup package" or whatever it's called. It's supposed to be on a separate 4MB partition on your hard drive, but if not, it will run from floppy as well.